Pen



FIG. 1 is an upper front right perspective view of a pen showing our new design;

FIG. 2 is an exploded lower left perspective view of the pen shown in FIG. 1, with the pen tip shown in broken lines illustrating environment and forming no part of the claimed design;

FIG. 3 is a left side elevation view of the pen shown in FIG. 1;

FIG. 4 is a top plan view thereof;

FIG. 5 is a front elevation view thereof;

FIG. 6 is a right side elevation view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is a rear elevation view thereof. 

The ornamental design for a pen, as shown and described. 